2.0 Analysis 2.1 Weather and Environment Other pilots flying in the area at the time of the occurrence indicated that they experienced light winds and little or no turbulence. There was no other significant weather in the area. Because it was the pilot's fourth trip of the day, he was familiar with the area of operation, the mission to be carried out, and the in-flight conditions. It is not likely that weather adversely affected the flight. 2.2 Aircraft Malfunction Records indicate that the aircraft was certified and equipped in accordance with existing regulations and procedures. The aircraft and wreckage were examined to the degree possible, and no evidence of a malfunction was found. It is unlikely that a mechanical failure of an aircraft component or system affected the occurrence. 2.3 Personnel Factors Records indicate that the pilot was certified and qualified for the flight in accordance with existing regulations. Based on the autopsy and toxicological information, and medical records, there was no evidence that incapacitation or physiological factors affected the pilot's performance. The pilot had several years experience in aerial application operations; however, he had only gained about 35 hours flying experience on the Dromader aircraft. 2.4 Aircraft Handling and Performance While the operator's flight evaluation of the aircraft at 12,500 lb did not indicate adverse handling characteristics, the approved aircraft flight manual indicates that, for operations at 11,700 lb in a fire-fighting configuration, hopper loading must be modified to control rearward C of G travel and that dynamic longitudinal instability may be experienced. The weight of the aircraft was approximately 12,115 lb, compared to the 11,700 lb fire-fighting configuration; the effect of the additional 415 lb and the agricultural spray configuration could not be quantified. However, a comparison of the aircraft characteristics and limitations in the basic flight manual and those specified in the approved supplement to the flight manual for operations to 11,700 lb indicates that there is a proportional deterioration of the handling characteristics with increased weight. In particular, the flight manual warns about the reduction in the aircraft's dynamic longitudinal stability, and the increased minimum manoeuvring speed because of a reduction in elevator control forces, and states that flying the aircraft below 106 mph requires the increased attention of the pilot. The deterioration of the flying characteristics of the aircraft demonstrates that operation at heavy weights is significantly more challenging and explains the flight manual's minimum pilot experience requirement of 200 hours on type for operations to 11,700 lb. The stall speed chart (see Section 1.16.3) shows the increase in the aircraft's stall speed, in level flight, with both weight and bank angle. The increase in stall speed reduces the flight speed envelope within which the aircraft may be operated. The high operating weight at the time of the occurrence would have significantly reduced the flight envelope of the aircraft, increased the likelihood of a stall, and adversely affected the aircraft's handling characteristics by decreasing the aircraft's dynamic stability and by increasing the stall speed. 2.5 Overload Operations There are a number of inconsistencies between the AFM and the OMS published for operations up to 12,500 lb (see Appendix B). The C of G range, load factor limits, and some of the airspeeds specified in the OMS conflict with the more restrictive AFM limits for operations at a lower weight. The OMS also does not indicate any limitation or performance changes with various aircraft configurations, such as the agricultural spray configuration. The warnings and manufacturer recommendations contained in the flight manual regarding operation at 11,700 lb, and the prohibition from operating in the agricultural configuration at more than 10,340 lb were not reflected in the OMS for operation at 12,500 lb, nor was the 120 mph maximum operating speed with the agricultural spray booms. Despite these inconsistencies, Transport Canada issued an exemption from Air Regulations subsection 210(1) and paragraph 218(a) permitting operation of the aircraft at a higher weight than allowed by the manufacturer's type approval. 2.6 Accident Sequence Without direct evidence of the actual events that occurred in the cockpit of the aircraft immediately prior to it entering the spin, it is not possible to conclusively determine why the aircraft stalled and spun. However, the high operating weight adversely affected the aircraft's handling characteristics by decreasing the aircraft's dynamic stability and increasing the stall speed in level flight, thereby increasing the likelihood of a stall. The pilot's relatively low level of experience on the aircraft type may have affected his ability to recognize the specific cues indicative of an impending stall condition and react in sufficient time to maintain aircraft control. As a result, it is likely that the pilot, while manoeuvring the aircraft overhead his assigned sector, did not recognize the cues of an impending stall and inadvertently allowed the aircraft to stall and enter a spin. Once the aircraft had departed controlled flight, there was insufficient altitude for the pilot to regain control of the aircraft prior to impact. 3.0 Conclusions 3.1 Findings It is unlikely that weather adversely affected the flight. Records indicate that the aircraft was certified and equipped in accordance with existing regulations and procedures. The aircraft and systems were examined to the degree possible, and no evidence of a malfunction was found. It is unlikely that a mechanical failure of an aircraft component or system affected the occurrence. There was no evidence of an in-flight fire; however, a post-crash fire ensued. The pilot was certified and qualified for the flight in accordance with existing regulations. Based on the autopsy, toxicology information, and medical records, there was no evidence that incapacitation or physiological factors affected the pilot's performance. The pilot had several years experience in aerial application operations; however, he had only gained about 35 hours flying experience on the Dromader aircraft. The weight and balance of the aircraft adversely affected the aircraft's handling characteristics by decreasing the aircraft's dynamic stability and by increasing the stall speeds. It is possible that the pilot did not recognize an impending stall and allowed the aircraft to stall and enter a spin. The aircraft stalled and entered a spin at too low an altitude to permit recovery. Despite the inconsistencies between the OMS that was published for operations up to 12,500 lb and the more restrictive AFM limits for operations at lower weights, Transport Canada issued an exemption from Air Regulations subsection 210(1) and paragraph 218(a) permitting operation of the aircraft at a higher weight than allowed by the manufacturer's type approval. 3.2 Causes The aircraft stalled and entered a spin at too low an altitude to permit recovery. Contributing to the occurrence was the reduction of the aircraft's handling characteristics and flight envelope that resulted from the operation of the aircraft at a higher weight than allowed by the manufacturer's type approval, as authorized by a special exemption program for agricultural operators. 4.0 Safety Action 4.1 Action Taken 4.1.1 Maximum Take-off Weight Exemptions On 23 June 1995, the TSB forwarded an Aviation Safety Advisory Letter to Transport Canada. The letter suggests that Transport Canada may wish to reassess the exemptions granted under the weight exemption program, and to review the overall adequacy of the program.